Figure 1. Density of apoptotic cells in zebra mussels infected or not by microparasites and their gonadal development stage.

(A) Mean number of apoptotic cells per mm² of tissue in non-infected zebra mussels, infected by ciliates Ophryoglena spp. (Oph), or by intracellular bacteria Rickettsiales-like organisms (RLO), or co-infected by these two parasites (Oph-RLO) (+ S.D.). (B) Percentages of mussels at each gamete development stage and gonadal index values (white dots). The host gender was also taken into account. Significant differences between groups of a same gender are indicated by different letters. The star indicates a significant difference between non-infected organisms (one-way ANOVA, Duncan’s post hoc test).